nix-closure-report

ncr reports evaluation time and closure size for NixOS, nix-darwin, Home Manager, and system-manager configurations.

Quick start

Run without installing NCR:

nix run github:greyxp1/ncr /path/to/flake

Installation

Add NCR as a flake input:

ncr.url = "github:greyxp1/ncr";

Import its NixOS module and set your flake path:

{inputs, ...}: {
  imports = [inputs.ncr.nixosModules.default];
  programs.ncr = {
    enable = true;
    flake = "/path/to/your/flake";
  };
}

Usage

Command	Behavior
ncr	All current-system configurations from NCR_FLAKE, set by programs.ncr.flake
ncr <flake>	Use a flake path or URL
ncr [<host> ...]	One or more configuration names. Ex: ncr desktop laptop
ncr --<type>	Filter by nixos, home, nix-darwin, or system-manager
ncr --jobs N	Evaluate up to N configurations at once. Defaults to available CPUs
ncr --show-skipped	List other-system hosts without measuring them
ncr --all-systems	Attempt to evaluate, build, and measure other-system hosts too

Evaluation time

Evaluation time varies with system load and cache state, so the first run after garbage collection may take longer. Evaluating hosts in parallel can finish the report sooner while increasing each host’s evaluation time. For more consistent measurements, evaluate one host at a time or use --jobs 1 to run sequentially.

Private binary caches

NCR uses your Nix cache settings and credentials. Binary caches can avoid builds, but each selected configuration still needs evaluation.

Testing

Run all checks:

nix develop -c ./tests/integration.sh